Environmental protection is becoming increasingly important. As our understanding of contamination of soil and water beneath the surface grows, our efforts to prevent leaks increases. Early efforts resulted in glass fiber reinforced plastic (hereinafter "FRP", single wall underground tanks, as described in U.S. Pat. No. 3,661,294 issued in 1972. As our awareness grew, our efforts to protect the environment matured into glass fiber reinforced plastic double-wall underground tanks, often equipped with leak detection systems, as described in U.S. Pat. No. 4,561,292 issued in 1985.
Others have attempted to encase or fit rigid storage tanks with secondary containment systems, often with flexible bladders or jackets, as described in U.S. Pat. No. 4,524,609 issued in 1985. Flexible bladders have obvious problems. For example, flexible inner bladders or flexible outer jackets are very susceptible to damage from cutting, tearing, puncturing, etc. Further, they require support, either through hoops or other mechanical features or by a vacuum system.